You've screened them for Technical, Business and Interpersonal skills. But are you done? There are many other steps you should be considering, including
1 - Do you check how many layers of vendors are there between you (the client) and the actual individual who will be performing services for you. I feel the number should be 1 or 2. I've heard some of my clients voice that the number should only be 1, to which I disagree. No one vendor has access to all Consultant resources, and they frequently work with subcontractors with certain niche skill sets. These vendors have invested time and resources into building a realtionship with, and screening from a large pool of subcontractors. So if you believe that the layer number should be only 1, you may be missing out on a larger talent pool available through the vendor's subcontractor network.
2 - Did you do only conduct Phone interview? We've heard stories of "Bait and Switch" i.e. a client interviews a candidate on the phone, hires the candidate, but a different candidate shows up on their first day. I understand that there are issues interviewing candidates who are located on the opposite side of the country. My in my experience, video interviews using free technology like Skype has proven beneficial. You may use Skype video + telephone simulataneously (disable Skype audio, or putting your PC speakers down), to improve the interview experience. There are other 'pay for' solutions available for video interviews. Which one you use is less important than using one.
3 - Did you give them an Online Technical Test - Again, I have heard stories of "Bait and Switch". One candidate takes the online test, and a different candidate shows on their first day. Considering the scenario that the candidate may be located on the opposite side of the country, what are you supposed to do? I personally like interviewing candidates and asking them questions for which there are no online tests. I talk to them about my project, and explain to them one particular issue I may be having. I look for their thought process, mastery of overall subject. I give them points even if the answer to the problem is incorrect, as long as they show their mastery of the subject matter. Why? I feel anyone can Google any question, and find the correct answer. What I am looking for is not the correct syntax for a line of code, but their ability to understand a problem, and then their thought process on their approach to solving the problem
4 - There have been some projects where my needs were to screen candidates for the 'syntax'. In this case, Id did a screen share with them - and showed them our code. And them I let them control my PC. What I was looking for was to see how quickly they can grasp the code. Then I asked them for suggestions on improving the code. I felt this process assessed their critical thinking, and problem solving skills.
5 - Where's their immediate family / spouse / children etc. Does their spouse work? What I learnt was most of us are not single and have some attachments to some people in our lives. I've noticed that when you remove people from these attachments, and the distance is large, there is turnover. So this is something I am always curious about
6 - Don't waste time on Reference checks - I feel 7 out of 10 candidates give references of people who will give them good references. So if you want to ask a reference "How were they at their job" expect an answer "Great". While I still see a value of reference checks, but getting accurate references can sometimes be very difficult. Sometimes insisting on this has resulted in me loosing some good candidates, where my competition hired that resource before I could finish reference checks. So if I have a need to check references, and I absolutely can't do without it, I would look at employers/projects where a candidate may have worked, and do my independent investigation on the candidate, calling people from my personal network, rather than relying on a reference provided by a candidate.
7 - Impose minimum wage rate to the actual assigned personnel working on your site. If the vendor tells you a bill rate of $100/hr. but is paying the assigned personnel $25/hr., you can bet that you will not have that candidate working at your site for too long. The candidate will soon find another opportunity that pays them a fair market value. Most consultants are fairly well educated about their market value, but sometimes circumstances lead them to 'accept' your assignment, only to see them leave within a couple of months. So I like to see in my contracts that the assigned personnel is getting paid a fair market value, which could vary between 40% to 80% of the bill rate (depending on layers, and whether you are hiring a Deloitte consultant or an IIT Consultant). I wouldn't impose on vendors a number like 80%, but different vendors have different costs. But sometimes I do ask them about their costs, and what percent of bill rate goes to the assigned personnel. My vendors work hard, and they deserve to make a living, and as long as I get a fair rate, I just want them not to abuse the assigned personnel.
8 - Ask candidates if they have any planned time off / vacations. This area is sometimes overlooked. Imagine hiring a consultant, who has a wedding planned right when you have your major roll out planned.
9 - Honestly identify who you 'really' are - Is your company a Tier-1 player, Tier-2 player etc... hire a consultant at the same level as you.. Lets say you are Google or Apple, then you can afford to hire a Tier-1 consultant. But if you are not, and want longevity in assigned personnel, get realistic about your expectations. I feel you can hire mediocre people, put them in a good environment with excellent processes, and receive 'superior' work. So invest in your process, culture and environment, and hire personnel that are a good fit. And in many circumstances, superstars are not a good fit in various environments.
10 - Don't hire friends / family / close referrals.. They are hard to fire.. I don't think I need to comment more on this subject
11 - Give interviewed candidate a takeaway question, and ask them to email you back with a response (don't propose a deadline) (see how soon they respond, and look at quality of their written and their analytical skills further)
I am sure there are many other ideas out there, to improve this process further. Do you have one?